Oxygen control systems and methods for combustion engines are well known in the art, for instance from U.S. Pat. No. 7,117,078. In conventional internal combustion engines there are an exhaust gas recirculation (EGR) system, an air mass sensor (or air flow meter), a pressure sensor and one or more temperature sensors.
The EGR system includes a controllable EGR valve able to modulate the gas flow from the exhaust manifold to the intake manifold. The recirculation gas can be taken in any point of the exhaust line, for example downstream the turbine or downstream the after-treatment point and the gas can be reintroduced into any point of the intake line, for example upstream one or more compressors or of the intercooler.
The air mass sensor is able to measure the fresh air flow entering the intake manifold through a throttle valve. The pressure sensor is able to measure the pressure of the gas and is placed in the intake manifold downstream the mixing point between the fresh air flow and the recirculated gas flows.
As stated above, there may be only one or more temperature sensors. If there is only one sensor (hardware configuration 1—HW1), it is placed in the intake manifold downstream the mixing point of the fresh air and the recirculated gas flows; if there are two sensors (hardware configuration 2—HW2), they can be placed near the throttle and the EGR valve. In conventional engines there is an electronic control unit arranged to estimate the fuel flow injected into the cylinders (software configuration 1—SW1), as well as the gas flow through the EGR valve (software configuration 2—SW2).
Known oxygen control systems evaluate the intake oxygen concentration assuming fluid-dynamic steady state conditions; the main drawback of this approach is the lack of precision in the oxygen concentration tracking during transient operations.
In view of the above, it is at least one object of the present invention to provide an improved method for estimating the intake oxygen concentration in combustion engines in both steady state and transient conditions. In addition, other objects, desirable features, and characteristics will become apparent from the subsequent detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.